Bizarre Problem - Will Not Idle!

[waehrik]

Alright, so another followup since this issue is still frustratingly not solved.

This past weekend I rebuilt the hall effect sensor with all new high temperature-safe teflon wires as my theory was that one of the two ignition triggers was not sending a signal back to the Motronic box. That would cause a lean condition since the injectors would not spray one of the two half-pulses per crank rotation. The spark would still happen at the right time on both cylinders due to the wasted spark system. Unfortunately that wasn't the problem and the bike behaves the exact same and doesn't idle.

I also replaced all of the in-tank fuel lines and fuel filter and that didn't do anything either.

So I'm still stuck!

 

[DougRaymond]

Baffling, I'm hoping you find the cause.
I appreciate your oscilloscope data, am trying to figure why the pulses are so erratic.
Shouldn't you try a slower time scale? I think you set it at 2s/division, did you try around 200ms/div?
I had to fiddle with my scope time setting for quite a while before I got a recognizable pulse train. Unfortunately the bike is down for now, can't repeat the measurements yet.

The fuel injector signal pulls the low side of the injector from 12v to 0v, once per crank revolution (I believe). At 1100rpm that should be 18 pulses per second, or 55milliseconds between pulses.

I wish someone knowledgeable could explain how the two HES sensors (TDC and BDC) are used. Theoretically, only the TDC sensor should be needed on a 4-cycle engine. Firing once per crank rev gives the wasted spark, which we know is the case. I doubt (but do not know) that the BDC sensor 'triggers' anything at all. Perhaps it is used to get a quicker read of RPM change?

What is sure is that both plugs and both injectors fire together. My unproven guess is that these are both triggered from TDC sensor only. Eager to know.

Good luck

 

[Troutluck]

Really dirty BBSs?

 

[waehrik]

Well I can finally follow up with a solution!

I had to surrender and drop the bike off at Max BMW in NH to diagnose the problem since I ran out of solutions. They plugged their diagnostic system into the bike and found that there was an open in the wiring harness to the throttle position sensor, which was causing the entire problem. Thus it was both a fuel and spark issue, just not from any of the sources that we thought!
$177 and the bike is fixed, I'm picking it up tomorrow

Just wanted to report back since so many people here have been interested in the saga. Unfortunately I can't think of any way of testing for this issue besides the BMW diagnostic system. My TPS worked fine when testing voltages at the connector but obviously a wiring harness issue doesn't let the Motronic see the correct reading. Since the voltages are only present when the bike is powered on, one would have to probe the main Motronic connector.

 

[acejones]

Seems like a remarkably cheap fix. If you added up all the time you spent on this and billed yourself at the going shop rate, You'd have to sell the bike to pay the bill.

 

[waehrik]

Seems like a remarkably cheap fix. If you added up all the time you spent on this and billed yourself at the going shop rate, You'd have to sell the bike to pay the bill.

Yep but my time is free, that's the beauty of working on it myself In parts I've spent less than $200 on this issue and that's not including selling back the throttle bodies that were working.

Though I like to think about it a different way - what if I didn't do all of this diagnostic work first? How long would it have taken the dealership to do all of these tests and how much higher would my bill have been? I gave them a page long list of everything I had tested and every modification made to the bike, which presumably narrowed the search.

 

[DougRaymond]

Congratulations, and thanks for reporting the solution- a busted TPS harness, who'd a thought?

Score one for supporting your local dealer, and letting him support you!

Also makes me want to buy a GS-911 to read sensor failures at home.

Otherwise, I too wonder how one would diagnose this at home. Wiggle test and close wire inspection might find it, maybe not.

Did dealer replace the TPS? I'd be surprised if they just mended the broken harness wire.

 

[waehrik]

Congratulations, and thanks for reporting the solution- a busted TPS harness, who'd a thought?

Score one for supporting your local dealer, and letting him support you!

Also makes me want to buy a GS-911 to read sensor failures at home.

Otherwise, I too wonder how one would diagnose this at home. Wiggle test and close wire inspection might find it, maybe not.

Did dealer replace the TPS? I'd be surprised if they just mended the broken harness wire.

If the GS-911 worked on my bike I'd already have one! Just with this one basic trip to the dealer it would have paid for itself. I've got the BMW special code reader for my e30 and e46 cars and it's come in very handy.

When I did my ABS wiring modification to eliminate the dreaded flashing lights during cold (winter) starts I checked all of the wiring and it looked great. Even when I rebuilt the wires on the hall effect sensor and replaced them with Teflon high temp wires the originals looked fine.

I actually had replaced the TPS with the one from the spare set of throttle bodies I had and it didn't make a difference. Probing the TPS wires themselves gave the correct outputs so it seems the open was on one of the signal wires and not on the power or ground. That would also explain why when I rotated the TPS way out of spec to make the engine richer (think the throttle bodies were further open) the bike could idle reliably but stalled as soon as I actually opened the throttle. I had taken that to indicate a fueling issue, which it really was, but the root cause was the wiring from the TPS. Now I can sell that extra TPS since I have two known good working ones

 

[happy wanderer]

Before buying a GS 911 take a very close look at what it can do with the 1100 series vs the 1150 series. A friend of mine has one for his 1150 GS and he can see all sorts of wonderful things like the temperatures of the sensors, the TPS reading on a nice bar graph and a host of other great tuning and trouble shooting data.

But when connected to the 1100 most of this stuff is not available. Just the basic fault codes and not much else.

The Motronic controllers are not the same in these bikes and the software functionality of his GS911 on his 1150 vs my 1100 is vastly better and more useful. Still though, it is a great device for reading fault codes quickly and easily.

 

[DougRaymond]

In principle, you can read the MCU diagnostic codes on the 3-pin diagnostic connector on the R1100 bikes.

I don't have an R1100 and haven't verified this, but supposedly reading Pin 1 with an analog volt meter shows the blip pattern that you can convert to numbers. And Pin 3 should do the same for ABS faults.

Can anyone testify to the usefulness (and correctness) of this R1100 feature?
Yes, it's stone age compared to the R1150 and later diagnostics.

 

[happy wanderer]

In principle, you can read the MCU diagnostic codes on the 3-pin diagnostic connector on the R1100 bikes.

I don't have an R1100 and haven't verified this, but supposedly reading Pin 1 with an analog volt meter shows the blip pattern that you can convert to numbers. And Pin 3 should do the same for ABS faults.

Can anyone testify to the usefulness (and correctness) of this R1100 feature?
Yes, it's stone age compared to the R1150 and later diagnostics.

+1 on that Doug. GSAddict and I played with his GS911 on his 1150 and then on my 1100. Needless to say, the output from my bikes was terribly disappointing and I would not spend that kind of money just to read what it puts out!

 

[m_stock10506]

I don't have an R1100 and haven't verified this, but supposedly reading Pin 1 with an analog volt meter shows the blip pattern that you can convert to numbers. And Pin 3 should do the same for ABS faults.

Just to correct this, ABS Fault codes and Reset are read and set with Pin 2, the center pin.

 

[DougRaymond]

Just to correct this, ABS Fault codes and Reset are read and set with Pin 2, the center pin.

Right you are, thanks.